1. Field of the Invention
This invention relates to on-board load measuring systems and more particularly to a load cell positioned between the bunk-supporting cross-beams and the frame of a logging tractor or trailer to measure the load carried by the logging truck.
2. Description of the Prior Art
On-board load measuring systems for logging trucks employing a load cell positioned between the bunk-supporting cross-beams and the frame of logging tractors and vehicles have been in use for several years. One such product is described in U.S. Pat. No. 4,020,911 issued to English et al and asigned to Structural Instrumentation, Inc. This system includes an elongated beam having its ends secured to a support plate which is, in turn, mounted on the frame of a logging tractor or trailer. The midportions of the beams are connected to the bunk-supporting cross-bar by a cross-bar support plate which is welded to the center portion of the beam. Strain guages mounted on the undersides of the beams between the ends and midsection measure load induced deflection of the beam.
The above-described load cell has greatly improved the ability of truckers to carry the maximum load allowed by law and thus represent a great improvement in the on-board load measuring field. However, under some extreme loading and/or operational conditions the cross-beam support plate, whether it is welded to or integral with the beam, can separate from the beam, sometimes causing the load to be dumped onto the road. Also, the thickness of the load cell spaces the bunk-supporting cross-beams above the frame of the tractor or trailer a corresponding distance thereby raising the center of gravity of the combination of log truck and load. Since logging trucks frequently travel over curved, irregular roads, it is desirable for the center of gravity to be as low as possible.